Vibratory spiral conveyors are generally known in the art. Such apparatus typically includes a spiral deck, formed in the shape of a helix, and a source of vibration operatively coupled to the deck. The spiral conveyor may be a brute force system, such as that disclosed in U.S. Pat. No. 2,927,683 to Carrier, or a two-mass system, as disclosed in U.S. Pat. No. 5,024,320 to Musschoot.
Spiral conveyors are often used to heat or cool work pieces or granular material. With foundry castings, for example, red hot castings (which may have a temperature of approximately 1000 degrees F. or more) are fed into the spiral conveyor. Cool air is directed over the castings as the castings travel up the spiral, thereby to reduce the temperature of the castings. Conventional spiral conveyors direct air from a center axis of the conveyor outwardly, with or without nozzles for directing the air toward the castings. The air is exhausted out an exterior of the spiral conveyor.
In one conventional design, air is generally directed radially across the spiral conveyor from the center core inlets to the outer periphery outlets. As a result, the inner facing side of the castings (or the inner row, should more than one row of castings be fed into the conveyor) will receive a lower temperature air than the outer facing side (or outer row).
In another conventional design, both the air inlet and air outlet are positioned at the outer periphery of the spiral conveyor. As the air enters the spiral conveyor area, it passes about the center core in at least two separate sub-streams. The air then exhausts from the spiral conveyor through a common outlet.
In addition, the deck used in conventional spiral conveyors is typically constructed of plate steel. As a result, when viewed in cross-section, the conveying surface defined by the deck is typically “flat” across the width of the deck. Stated alternatively, the conveying surface is substantially linear across its width.
While a flat deck is satisfactory for many applications, it may cause unintended and undesirable results when used to convey certain objects. For example, when conveying generally cylindrical objects such as cam shafts along a flat deck, the objects may roll transversely across the width of the deck, and therefore are not located on the deck with any degree of certainty. In addition, the cylindrical objects may become oriented transversely across the deck, and therefore more easily roll into and possibly damage other objects on the deck.
Flat decks are also difficult to employ for certain path configurations. In a spiral conveyor, for example, it is preferable to form the deck in a helicoid shape. To approximate the helicoid shape with flat plate steel, several bends such as cross crimps are typically formed in the deck. Such cross crimps, however, create abrupt changes in the pitch of the deck and cause the conveying surface to be non-linear across its width. Consequently, the cross-crimps create localized high wear area and non-uniform stresses in the deck. These problems are exacerbated during thermal expansion and contraction, which can be significant when the spiral conveyor is used for heating or cooling of the objects being conveyed. In addition, the need for cross crimps or other bends in the deck increases manufacturing costs and makes assembly more difficult, especially for conveyors that are constructed as multiple sub-assemblies that are mated together, such as for large conveyor sizes.